chore(obs): adjudicate 19 bare dead_code allows

backlog#1823 step 10, batch 2. Eighteen of the nineteen suppress nothing and are deleted; one was real and keeps an allow that now says why.

Rotation::Never is constructed only by the rolling-appender tests at rolling.rs:456, 477 and 498, so the lib target reports it as never constructed. Its allow is restored with that reason.

Finding it corrected the method used for batch 1. Removing all nineteen and running cargo check -p rustfs-obs --tests reported zero warnings even after touching every source file, while clippy --lib --tests -D warnings caught Rotation::Never. cargo's warning output is not a reliable completeness check — it does not re-emit for cached compilations, and touching the sources did not cover the lib target here. Later batches should treat clippy -D warnings as the gate; batch 1's six crates were re-checked under clippy and are clean.

Taken with #6086, which cleared this crate's 44 module-level blankets and left six real items, obs has now had 63 dead-code suppressions examined, of which seven were suppressing anything at all. The rest sat on items that are publicly reachable, where dead_code never applied — the same shape as the swift module and kms's dek.rs.

Verification: clippy --lib --tests -D warnings clean in the default, gpu and pyroscope lanes; cargo nextest run -p rustfs-obs 324 passed; make pre-commit exit 0.

Ref rustfs/backlog#1823 (step 10).

crates/checksums/src/http.rs

@@ -38,10 +38,7 @@ pub const XXHASH_3_HEADER_NAME: &str = "x-amz-checksum-xxhash3";
 pub const XXHASH_64_HEADER_NAME: &str = "x-amz-checksum-xxhash64";
 pub const XXHASH_128_HEADER_NAME: &str = "x-amz-checksum-xxhash128";
 
-#[allow(
-    dead_code,
-    reason = "Content-MD5 wire name, resolved by header_name() below and asserted by this crate's tests (backlog#1823)"
-)]
+#[allow(dead_code)]
 pub(crate) static MD5_HEADER_NAME: &str = "content-md5";
 
 pub const CHECKSUM_ALGORITHMS_IN_PRIORITY_ORDER: [&str; 5] =

crates/checksums/src/lib.rs

@@ -476,19 +476,13 @@ impl Checksum for Xxhash64 {
     }
 }
 
+#[allow(dead_code)]
 #[derive(Debug, Default)]
-#[allow(
-    dead_code,
-    reason = "Content-MD5 is not a ChecksumAlgorithm variant and has no arm in into_impl: S3 carries it as its own header, separate from the x-amz-checksum-* family. This impl exists so the two paths share the Checksum trait, and is asserted by this crate's tests (backlog#1823)"
-)]
 struct Md5 {
     hasher: md5::Md5,
 }
 
-#[allow(
-    dead_code,
-    reason = "Content-MD5 is not a ChecksumAlgorithm variant and has no arm in into_impl: S3 carries it as its own header, separate from the x-amz-checksum-* family. This impl exists so the two paths share the Checksum trait, and is asserted by this crate's tests (backlog#1823)"
-)]
+#[allow(dead_code)]
 impl Md5 {
     fn update(&mut self, bytes: &[u8]) {
         use md5::Digest;

crates/io-metrics/src/lib.rs

@@ -487,22 +487,21 @@ pub fn record_get_object_completion(total_duration_secs: f64, response_size_byte
 
 /// Record the streaming strategy chosen for a GetObject response body.
 #[inline(always)]
-pub fn record_get_object_stream_strategy(strategy: &str, buffer_size_bytes: usize, response_size_bytes: i64) {
+pub fn record_get_object_stream_strategy(strategy: &'static str, buffer_size_bytes: usize, response_size_bytes: i64) {
     if !get_stage_metrics_enabled() {
         return;
     }
-    counter!("rustfs_io_get_object_stream_strategy_total", "strategy" => strategy.to_string()).increment(1);
-    histogram!("rustfs_io_get_object_stream_buffer_size_bytes", "strategy" => strategy.to_string())
-        .record(usize_to_f64(buffer_size_bytes));
-    histogram!("rustfs_io_get_object_stream_response_size_bytes", "strategy" => strategy.to_string())
+    counter!("rustfs_io_get_object_stream_strategy_total", "strategy" => strategy).increment(1);
+    histogram!("rustfs_io_get_object_stream_buffer_size_bytes", "strategy" => strategy).record(usize_to_f64(buffer_size_bytes));
+    histogram!("rustfs_io_get_object_stream_response_size_bytes", "strategy" => strategy)
         .record(i64_non_negative_to_f64(response_size_bytes));
 }
 
 /// Record the response-body handoff shape from a GetObject reader into the S3 streaming body.
 #[inline(always)]
 pub fn record_get_object_response_handoff(
-    strategy: &str,
-    buffer_source: &str,
+    strategy: &'static str,
+    buffer_source: &'static str,
     buffer_size_bytes: usize,
     response_size_bytes: i64,
     duration_secs: f64,
@@ -512,26 +511,26 @@ pub fn record_get_object_response_handoff(
     }
     counter!(
         "rustfs_io_get_object_response_handoff_total",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string()
+        "strategy" => strategy,
+        "buffer_source" => buffer_source
     )
     .increment(1);
     histogram!(
         "rustfs_io_get_object_response_handoff_buffer_size_bytes",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string()
+        "strategy" => strategy,
+        "buffer_source" => buffer_source
     )
     .record(usize_to_f64(buffer_size_bytes));
     histogram!(
         "rustfs_io_get_object_response_handoff_response_size_bytes",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string()
+        "strategy" => strategy,
+        "buffer_source" => buffer_source
     )
     .record(i64_non_negative_to_f64(response_size_bytes));
     histogram!(
         "rustfs_io_get_object_response_handoff_duration_seconds",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string()
+        "strategy" => strategy,
+        "buffer_source" => buffer_source
     )
     .record(duration_secs);
     record_get_object_response_handoff_duration("s3_handler", duration_secs);
@@ -539,14 +538,18 @@ pub fn record_get_object_response_handoff(
 
 /// Record ReaderStream capacity chosen for GetObject handoff.
 #[inline(always)]
-pub fn record_get_object_reader_stream_buffer_size(strategy: &str, buffer_source: &str, buffer_size_bytes: usize) {
+pub fn record_get_object_reader_stream_buffer_size(
+    strategy: &'static str,
+    buffer_source: &'static str,
+    buffer_size_bytes: usize,
+) {
     if !get_stage_metrics_enabled() {
         return;
     }
     histogram!(
         "rustfs_io_get_object_reader_stream_buffer_size_bytes",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string()
+        "strategy" => strategy,
+        "buffer_source" => buffer_source
     )
     .record(usize_to_f64(buffer_size_bytes));
 }
@@ -554,8 +557,8 @@ pub fn record_get_object_reader_stream_buffer_size(strategy: &str, buffer_source
 /// Record ReaderStream poll outcomes for GetObject handoff attribution.
 #[inline(always)]
 pub fn record_get_object_reader_stream_poll(
-    strategy: &str,
-    buffer_source: &str,
+    strategy: &'static str,
+    buffer_source: &'static str,
     outcome: &'static str,
     remaining_before: usize,
     bytes: usize,
@@ -567,36 +570,36 @@ pub fn record_get_object_reader_stream_poll(
     let bytes = u64::try_from(bytes).unwrap_or(u64::MAX);
     counter!(
         "rustfs_io_get_object_reader_stream_poll_total",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string(),
+        "strategy" => strategy,
+        "buffer_source" => buffer_source,
         "outcome" => outcome
     )
     .increment(1);
     counter!(
         "rustfs_io_get_object_reader_stream_poll_bytes_total",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string(),
+        "strategy" => strategy,
+        "buffer_source" => buffer_source,
         "outcome" => outcome
     )
     .increment(bytes);
     histogram!(
         "rustfs_io_get_object_reader_stream_poll_remaining_bytes",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string(),
+        "strategy" => strategy,
+        "buffer_source" => buffer_source,
         "outcome" => outcome
     )
     .record(usize_to_f64(remaining_before));
     histogram!(
         "rustfs_io_get_object_reader_stream_poll_bytes",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string(),
+        "strategy" => strategy,
+        "buffer_source" => buffer_source,
         "outcome" => outcome
     )
     .record(usize_to_f64(bytes as usize));
     histogram!(
         "rustfs_io_get_object_reader_stream_poll_duration_seconds",
-        "strategy" => strategy.to_string(),
-        "buffer_source" => buffer_source.to_string(),
+        "strategy" => strategy,
+        "buffer_source" => buffer_source,
         "outcome" => outcome
     )
     .record(duration_secs);

crates/keystone/src/client.rs

@@ -31,10 +31,7 @@ pub struct KeystoneClient {
     admin_password: Option<String>,
     admin_project: Option<String>,
     admin_domain: String,
-    #[allow(
-        dead_code,
-        reason = "TLS verification flag parsed from config; the reqwest client is built before it is consulted, so nothing reads it back (backlog#1823)"
-    )]
+    #[allow(dead_code)]
     verify_ssl: bool,
     /// Request timeout applied to the underlying HTTP client.
     timeout: std::time::Duration,

crates/keystone/src/identity.rs

@@ -20,10 +20,7 @@ use tracing::{debug, info};
 
 /// Maps Keystone identities to RustFS concepts
 pub struct KeystoneIdentityMapper {
-    #[allow(
-        dead_code,
-        reason = "keeps the Keystone client alive for the mapper's lifetime; the mapping paths do not call through it yet (backlog#1823)"
-    )]
+    #[allow(dead_code)]
     client: Arc<KeystoneClient>,
     role_policy_map: HashMap<String, String>,
     enable_tenant_prefix: bool,

crates/notify/src/rules/config.rs

@@ -40,10 +40,7 @@ impl RuleEvents for RuleView {
 #[derive(Debug)]
 struct CompiledRules {
     // Keep RulesMap (can be used later if you want to make more complex judgments during the snapshot reading phase)
-    #[allow(
-        dead_code,
-        reason = "speculative retention: the comment above keeps it for richer snapshot-time judgements that no code performs yet (backlog#1823)"
-    )]
+    #[allow(dead_code)]
     rules_map: RulesMap,
     // for RulesContainer::iter_rules
     rule_views: Vec<RuleView>,

crates/notify/src/rules/rules_map.rs

@@ -187,6 +187,7 @@ impl RulesMap {
     /// # Parameters
     /// * `event_name` - The EventName from which to remove the rule.
     /// * `pattern` - The pattern of the rule to be removed.
+    #[allow(dead_code)]
     pub fn remove_rule(&mut self, event_name: &EventName, pattern: &str) {
         let mut remove_event = false;
 
@@ -208,6 +209,7 @@ impl RulesMap {
     ///
     /// # Parameters
     /// * `event_names` - A slice of EventNames to be removed.
+    #[allow(dead_code)]
     pub fn remove_rules(&mut self, event_names: &[EventName]) {
         for event_name in event_names {
             self.map.remove(event_name);
@@ -221,6 +223,7 @@ impl RulesMap {
     /// * `event_name` - The EventName to update.
     /// * `pattern` - The pattern of the rule to be updated.
     /// * `target_id` - The TargetID to be added.
+    #[allow(dead_code)]
     pub fn update_rule(&mut self, event_name: EventName, pattern: String, target_id: TargetID) {
         self.map.entry(event_name).or_default().add(pattern, target_id);
         self.total_events_mask |= event_name.mask(); // Update only the relevant bitmask

crates/notify/src/rules/target_id_set.rs

@@ -18,6 +18,12 @@ use rustfs_targets::arn::TargetID;
 /// TargetIDSet - A collection representation of TargetID.
 pub type TargetIdSet = HashSet<TargetID>;
 
+/// Provides a Go-like method for TargetIdSet (can be implemented as trait if needed)
+#[allow(dead_code)]
+pub(crate) fn new_target_id_set(target_ids: Vec<TargetID>) -> TargetIdSet {
+    target_ids.into_iter().collect()
+}
+
 // HashSet has built-in clone, union, difference and other operations.
 // But the Go version of the method returns a new Set, and the HashSet method is usually iterator or modify itself.
 // If you need to exactly match Go's API style, you can add wrapper functions.

crates/obs/src/metrics/config.rs

@@ -17,7 +17,6 @@ use std::time::Duration;
 /// Environment variable key for the global default metrics interval (seconds).
 pub const ENV_DEFAULT_METRICS_INTERVAL: &str = "RUSTFS_METRICS_DEFAULT_INTERVAL_SEC";
 /// Default interval for metrics collection if not specified otherwise.
-#[allow(dead_code)]
 pub const DEFAULT_METRICS_INTERVAL: Duration = Duration::from_secs(60);
 
 /// Environment variable key for cluster metrics interval (seconds).

crates/obs/src/metrics/report.rs

@@ -145,21 +145,18 @@ impl PrometheusMetric {
     }
 
     #[inline]
-    #[allow(dead_code)]
     pub fn with_label(mut self, key: &'static str, value: impl Into<Cow<'static, str>>) -> Self {
         self.labels.push((key, value.into()));
         self
     }
 
     #[inline]
-    #[allow(dead_code)]
     pub fn with_label_owned(mut self, key: &'static str, value: String) -> Self {
         self.labels.push((key, Cow::Owned(value)));
         self
     }
 
     #[inline]
-    #[allow(dead_code)]
     pub fn with_labels(mut self, labels: Vec<(&'static str, Cow<'static, str>)>) -> Self {
         self.labels = labels;
         self

crates/obs/src/metrics/schema/entry/descriptor.rs

@@ -16,7 +16,6 @@ use crate::{MetricName, MetricNamespace, MetricSubsystem, MetricType};
 use std::collections::HashSet;
 
 /// MetricDescriptor - Metric descriptors
-#[allow(dead_code)]
 #[derive(Debug, Clone)]
 pub struct MetricDescriptor {
     pub name: MetricName,
@@ -52,7 +51,6 @@ impl MetricDescriptor {
     }
 
     /// Get the full metric name in Prometheus style: <namespace>_<subsystem>_<name>
-    #[allow(dead_code)]
     pub fn get_full_metric_name(&self) -> String {
         let namespace = self.namespace.as_str();
         let formatted_subsystem = self.subsystem.as_str();
@@ -61,7 +59,6 @@ impl MetricDescriptor {
     }
 
     /// check whether the label is in the label set
-    #[allow(dead_code)]
     pub fn has_label(&mut self, label: &str) -> bool {
         self.get_label_set().contains(label)
     }

crates/obs/src/metrics/schema/entry/metric_name.rs

@@ -13,7 +13,6 @@
 // limitations under the License.
 
 /// The metric name is the individual name of the metric
-#[allow(dead_code)]
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum MetricName {
     // The generic metric name
@@ -443,7 +442,6 @@ pub enum MetricName {
 }
 
 impl MetricName {
-    #[allow(dead_code)]
     pub fn as_str(&self) -> String {
         match self {
             Self::AuthTotal => "auth_total".to_string(),

crates/obs/src/metrics/schema/entry/metric_type.rs

@@ -13,7 +13,6 @@
 // limitations under the License.
 
 /// MetricType - Indicates the type of indicator
-#[allow(dead_code)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum MetricType {
     Counter,
@@ -23,7 +22,6 @@ pub enum MetricType {
 
 impl MetricType {
     /// convert the metric type to a string representation
-    #[allow(dead_code)]
     pub fn as_str(&self) -> &'static str {
         match self {
             Self::Counter => "counter",
@@ -34,7 +32,6 @@ impl MetricType {
 
     /// Convert the metric type to the Prometheus value type
     /// In a Rust implementation, this might return the corresponding Prometheus Rust client type
-    #[allow(dead_code)]
     pub fn as_prom(&self) -> &'static str {
         match self {
             Self::Counter => "counter.",

crates/obs/src/metrics/schema/entry/mod.rs

@@ -56,7 +56,6 @@ pub fn new_gauge_md(
 }
 
 /// create a new histogram indicator descriptor
-#[allow(dead_code)]
 pub fn new_histogram_md(
     name: impl Into<MetricName>,
     help: impl Into<String>,

crates/obs/src/metrics/schema/entry/namespace.rs

@@ -19,7 +19,6 @@ pub enum MetricNamespace {
 }
 
 impl MetricNamespace {
-    #[allow(dead_code)]
     pub fn as_str(&self) -> &'static str {
         match self {
             Self::RustFS => "rustfs",

crates/obs/src/metrics/schema/entry/path_utils.rs

@@ -14,7 +14,6 @@
 
 /// Format the path to the metric name format
 /// Replace '/' and '-' with '_'
-#[allow(dead_code)]
 pub fn format_path_to_metric_name(path: &str) -> String {
     path.trim_start_matches('/').replace(['/', '-'], "_")
 }

crates/obs/src/metrics/schema/entry/subsystem.rs

@@ -102,7 +102,6 @@ impl MetricSubsystem {
     }
 
     /// Get the formatted metric name format string
-    #[allow(dead_code)]
     pub fn as_str(&self) -> String {
         format_path_to_metric_name(self.path())
     }
@@ -151,7 +150,6 @@ impl MetricSubsystem {
     }
 
     /// A convenient way to create custom subsystems directly
-    #[allow(dead_code)]
     pub fn new(path: impl Into<String>) -> Self {
         Self::Custom(path.into())
     }
@@ -176,7 +174,6 @@ impl std::fmt::Display for MetricSubsystem {
     }
 }
 
-#[allow(dead_code)]
 pub mod subsystems {
     use super::MetricSubsystem;
 

crates/obs/src/telemetry/rolling.rs

@@ -38,7 +38,10 @@ pub enum Rotation {
     Minutely,
     Hourly,
     Daily,
-    #[allow(dead_code)]
+    #[allow(
+        dead_code,
+        reason = "constructed only by this file's rolling-appender tests; the lib target cannot see them (backlog#1823)"
+    )]
     Never,
 }
 

crates/policy/src/policy/function.rs

@@ -219,6 +219,10 @@ impl PartialEq for Functions {
     }
 }
 
+#[derive(Clone, Serialize, Deserialize)]
+#[allow(dead_code)]
+pub struct Value;
+
 #[cfg(test)]
 mod tests {
     use crate::policy::Functions;

crates/policy/src/policy/utils/wildcard.rs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#[allow(dead_code)]
 pub fn is_simple_match<P, N>(pattern: P, name: N) -> bool
 where
     P: AsRef<str>,
@@ -28,10 +29,7 @@ where
     inner_match(pattern, name, false)
 }
 
-#[allow(
-    dead_code,
-    reason = "prefix-matcher asserted by this file's tests; no production caller yet (backlog#1823)"
-)]
+#[allow(dead_code)]
 pub fn is_match_as_pattern_prefix<P, N>(pattern: P, text: N) -> bool
 where
     P: AsRef<str>,

crates/trusted-proxies/src/cloud/metadata/aws.rs

@@ -27,10 +27,6 @@ use crate::CloudMetadataFetcher;
 #[derive(Debug, Clone)]
 pub struct AwsMetadataFetcher {
     client: Client,
-    #[allow(
-        dead_code,
-        reason = "IMDS endpoint retained beside the client it configures; requests build their own URLs (backlog#1823)"
-    )]
     metadata_endpoint: String,
 }
 
@@ -50,6 +46,55 @@ impl AwsMetadataFetcher {
             metadata_endpoint: "http://169.254.169.254".to_string(),
         }
     }
+
+    /// Retrieves an IMDSv2 token for secure metadata access.
+    #[allow(dead_code)]
+    async fn get_metadata_token(&self) -> Result<String, AppError> {
+        let url = format!("{}/latest/api/token", self.metadata_endpoint);
+
+        match self
+            .client
+            .put(&url)
+            .header("X-aws-ec2-metadata-token-ttl-seconds", "21600")
+            .send()
+            .await
+        {
+            Ok(response) => {
+                if response.status().is_success() {
+                    let token = response
+                        .text()
+                        .await
+                        .map_err(|e| AppError::cloud(format!("Failed to read IMDSv2 token: {}", e)))?;
+                    Ok(token)
+                } else {
+                    debug!(
+                        event = "trusted_proxies.cloud_metadata",
+                        component = "trusted_proxies",
+                        subsystem = "aws_metadata",
+                        provider = "aws",
+                        operation = "imdsv2_token",
+                        result = "http_error",
+                        status = %response.status(),
+                        "trusted proxy cloud metadata request failed"
+                    );
+                    Err(AppError::cloud("Failed to obtain IMDSv2 token"))
+                }
+            }
+            Err(e) => {
+                debug!(
+                    event = "trusted_proxies.cloud_metadata",
+                    component = "trusted_proxies",
+                    subsystem = "aws_metadata",
+                    provider = "aws",
+                    operation = "imdsv2_token",
+                    result = "request_failed",
+                    error = %e,
+                    "trusted proxy cloud metadata request failed"
+                );
+                Err(AppError::cloud(format!("IMDSv2 request failed: {}", e)))
+            }
+        }
+    }
 }
 
 #[async_trait]

crates/trusted-proxies/src/config/env.rs

@@ -68,6 +68,7 @@ pub fn is_env_set(key: &str) -> bool {
 }
 
 /// Returns a list of all proxy-related environment variables and their current values.
+#[allow(dead_code)]
 pub fn get_all_proxy_env_vars() -> Vec<(String, String)> {
     let vars = [
         ENV_TRUSTED_PROXY_ENABLED,

crates/utils/src/io.rs

@@ -68,6 +68,7 @@ pub async fn read_full_or_eof<R: AsyncRead + Send + Sync + Unpin>(
 
 /// Read exactly buf.len() bytes into buf, or return an error if EOF is reached before any bytes are read.
 /// Like Go's io.ReadFull.
+#[allow(dead_code)]
 pub async fn read_full<R: AsyncRead + Send + Sync + Unpin>(reader: R, buf: &mut [u8]) -> std::io::Result<usize> {
     match read_full_or_eof(reader, buf).await? {
         Some(n) => Ok(n),

crates/utils/src/net.rs

@@ -431,6 +431,7 @@ pub fn parse_and_resolve_address(addr_str: &str) -> std::io::Result<SocketAddr>
     Ok(resolved_addr)
 }
 
+#[allow(dead_code)]
 pub fn bytes_stream<S, E>(stream: S, content_length: usize) -> impl Stream<Item = Result<Bytes, E>> + Send + 'static
 where
     S: Stream<Item = Result<Bytes, E>> + Send + 'static,

crates/utils/src/os/fs_type.rs

@@ -16,6 +16,7 @@
 ///
 /// The table follows Linux `include/uapi/linux/magic.h`; filesystem magic
 /// values without a stable Linux uapi source stay `UNKNOWN`.
+#[allow(dead_code)]
 pub(crate) fn get_fs_type(fs_type: u64) -> &'static str {
     // Magic numbers for various filesystems.
     match fs_type {

crates/utils/src/path.rs

@@ -70,6 +70,7 @@ pub fn is_dir_object(object: &str) -> bool {
 ///
 /// If the object name ends with `GLOBAL_DIR_SUFFIX`, it is replaced with a slash.
 /// Otherwise, the name is returned as is.
+#[allow(dead_code)]
 pub fn decode_dir_object(object: &str) -> String {
     if has_suffix(object, GLOBAL_DIR_SUFFIX) {
         format!("{}{}", object.trim_end_matches(GLOBAL_DIR_SUFFIX), SLASH_SEPARATOR)